1. Technical Field
The present invention relates to a liquid crystal device in which liquid crystals are held between a pair of substrates, and a projection-type display apparatus which uses the liquid crystal device as a light valve.
2. Related Art
In a liquid crystal device, an element substrate provided with an image display region having a plurality of pixel electrodes arranged on one surface side and a counter substrate provided with a common electrode to which a common potential is applied are bonded to each other by a seal material, and a liquid crystal layer is held in a region surrounded by the seal material between the element substrate and the counter substrate. In order to manufacture the liquid crystal device, first, when the seal material is applied to the element substrate in a frame form, a broken portion is provided, and after the element substrate and the counter substrate are overlapped with each other via the seal material, the seal material is cured. Then, a liquid crystal material is depressurized and injected between the element substrate and the counter substrate from the portion where the seal material is broken, a sealing material is applied to the broken portion, and the sealing material is cured.
In such a liquid crystal device, when ionic impurities infiltrating during liquid crystal injection or ionic impurities eluted from the seal material are aggregated in the image display region by driving the liquid crystal device, degradation of display quality such as burn-in (discoloration) of an image is caused. Consequently, a technique is suggested in which a peripheral electrode is provided on the outside of the image display region and ionic impurities are pulled into the peripheral electrode so as to be stayed, thereby preventing the ionic impurities from being aggregated in the image display region (refer to FIG. 4 and the like in JP-A-2008-58497).
More specifically, in the technique described in JP-A-2008-58497, a first peripheral electrode and a second peripheral electrode are provided to surround the periphery of an image display region, different potentials are applied to the first and second peripheral electrodes, and the polarities of the potentials applied to the first and second peripheral electrodes are reversed for each frame, such that due to a lateral electric field between the first and second peripheral electrodes, a little fluctuation of liquid crystals and movement of ionic impurities are performed. In this manner, the ionic impurities are pulled into the first and second peripheral electrodes so as to be stayed therein.
However, in the configuration described in JP-A-2008-58497, consideration for a structure unique to the liquid crystal device is not sufficiently made, so that there is a problem in that aggregation of ionic impurities in the image display region cannot be reliably prevented. More specifically, a seal material is cured before a liquid crystal material is sealed and thus can be cured under appropriate conditions for either light curing or thermal curing. Contrary to this, a sealing material is cured after the liquid crystal material is sealed and thus cannot be cured under appropriate conditions for either light curing or thermal curing from the viewpoint of prevention of deterioration of the liquid crystal material. Therefore, ionic non-reactive components are more likely to be released to the liquid crystal layer from the sealing material than the seal material. However, the peripheral electrodes described in JP-A-2008-58497 cannot reliably pull the ionic impurities generated from the sealing material so as to be stayed therein.